Beam-heated thermal relay



Feb. 17,1970 R; nossasn 3 3.4965

BEAM-HEATED THERMAL RELAY Filed Nov. 22, 196'? 2 sheets-sheet 1 X Y 2 a ,22

Y I o Fig.1

NVENTOR ROLF ROSSBERG ATTORNEY Feb. 17, '1970 R.. ROSSBERG 3,

BEAM-HEATED THERMAL RELAY Filed NOV. 22. 1967 2 ShetS-Sheet 2 INVENTOR 9- 5 ROLF aossasns ATTORNEY United States Patent 3,496,507 BEAM-HEATED THERMAL RELAY Rolf Rossberg, Korntal, Germany, assignor to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed Nov. 22, 1967, Ser. No. 685,057 Claims priority, application Germany, Dec. 2, 1966, St 26,192 Int. Cl. H01h 37/00, 61/00 U.S. Cl. 337-1 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The invention relates to a beam-heated thermal relay, particularly adaptable for use as a blinker or pulse generator with a low pulsing frequency, including a filament wire and a bimetallic contact influenced by the filament wire.

A number of thermal relays are known in the art for use as blinkers, but these have various disadvantages compared to the present invention. For example, German printed application No. 1,218,589 describes a blinker with a resistor which controls a switching element according to the current applied, wherein the contacts of the switching element serve not only to actuate the operating circuit, but also to switch the filament current on and off for controlling the resistor. The fact that the load contacts must actuate the operating circuit and the filament circuit simultaneously results in the disadvantage that the individual make-contact can be loaded only to the extent of the sum of the current flowing in both the operating circuit and the filament circuit, thereby reducing the amount of current which can be handled in the operating circuit. Moreover, the intricate construction of such a blinker is very expensive.

Another prior art device suitable to be used as a blinker or as a pulse sender is described in German printed application No. 1,181,299, this device being an electrothermic switching device in which the movable contact is actuated by an additionally provided bimetal strip which is bent under the heat effect of two current paths. This device has the disadvantage that the heat produced by both current paths must be substantially higher than that necessary to bend the bimetallic strip, because the heat is not only led to the bimetallic strip, but is radiated unchecked to all sides, whereby only a small portion of the quantity of heat produced hits the bimetallic strip. Additionally, the contact arrangement is loaded with the current producing the heat in both current paths.

SUMMARY OF THE INVENTION In the view of these and other problems in the art, it is an object of the present invention to avoid the disadvantages of prior art arrangements such as those mentioned above, and to provide a simply constructed thermal relay which requires only little heating power. This is achieved, according to the invention, by arranging the filament wire and a bimetallic contact strip in such a way that the filament wire and the bimetallic strip are located at the opposite focuses of an ellipse which is formed by the mirror-like inside surface of a cylindrical-shaped reflector, the longitudinal axis of which is parallel to the filament wire and also parallel to the longitudinal axis of the bimetallic strip.

Another object of the invention is to provide a thermal relay of the character described wherein the ellipse of the reflector is open on the side where the bimetal strip is provided, in such a way that both edges are parallel to the longitudinal axis of the reflector and approximately coincide with the parameter passing through the re spective focus of the ellipse.

A further object of the invention is to provide a thermal relay of the charatcer described wherein the metal of the bimetal strip with the higher extension coefiicient is provided on the side toward the inside of the ellipse, and the metal with the lower extension coeflicient is provided on the outwardly facing side of the bimetal strip.

Another object of the invention is to provide a thermal relay of the charatcer described wherein the filament wire is freely suspended.

Another object is to provide a thermal relay of the character described wherein the relay arrangement is hermetically sealed in a glass tube or glass bulb which Is preferably substantially free of oxygen as by evacuation or by being filled with a protective gas. The filament wire, bimetal contact and elliptical reflector may all be contained within the glass enclosure, or alternatively the glass enclosure may have an elliptical cross-section and be mirrored on its inside surface so as to form the reflector.

The present invention has a variety of advantages over previously known thermal relays. The filament circuit and the contact circuit can, if desired, operate completely independent of each other. It is also possible to operate the filament wire and the contacting means in series connection to a current source as a blinker, with the filament wire not only providing the heat for actuating the contacting means but also providing the luminescent part of the blinker.

By locating the filament wire and the bimetal strip in opposite focuses of an elliptic reflector, a high degree of efliciency of the entire arrangement is achieved, so that very little filament power is required. This is of particular importance if the filament wire and contracting means are series connected, as in a blinker arrangement. On one hand the flow of contact material particles increases with the current intensity or amperage and, on the other hand, the amperage increases according to the square of an increasing heat requirement on the filament wire. With the present arrangement, the heat produced along the filament wire must be only higher by the amount actually necessary for the bimetal strip, resulting from the small loss factor of the reflector. A particular advantage resulting from the small heat required is that the bimetal strip takes up heat at first only on one side, and this heat is completely suflicient to bend the bimetal strip. Consequently, the entire arrangement can be made very small. When the bimetallic strip is bent out of the focusing line of the elliptical reflector the heat furnished to the strip is automatically reduced. Accordingly, no excessive heating or excessive load on the bimetallic strip is possible, even during constant operation. Therefore, it is not necessary to reduce the filament power for short operating periods.

The invention is explained in detail with the aid of the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view illustrating a laboratory arrangement of the present invention.

FIGURE 2 is a diagrammatic view illustrating the reflector, filament wire and bimetallic strip portions of the relay, looking at these parts from the ends thereof, illustrating the principle of operation of the invention.

FIGURE 3 is a perspective view of the arrangement shown in FIGURE 2.

FIGURE 4 is a longitudinal section, partly in elevation, showing a thermal relay according to the present invention melted into a tubular-shaped glass body, in an arrangement similar to a reed switch.

FIGURE 5 is a fragmentary perspective view of the thermal relay in which the entire arrangement is accommodated on a glass socket, similar to the filament wire of an incandescent bulb.

FIGURE 6 is an elevational view showing a thermal relay according to the invention housed in a glass bulb, similar to bulbs used in conventional incandescent lamps.

DETAILED DESCRIPTION Referring at first to FIGURE 1 which shows a laboratory arrangement of the beam-heated thermal relay, plates 2 and 9 are fixed on opposite ends of a felt-paper support 10. Between said plates 2 and 9 a filament wire 3 is affixed with the aid of a leaf-type spring 1. Two spaced felt-paper plates 4 and 8 are fastened to the support 10 so as to extend upwardly therefrom, the plates 4 and 8 each having an aperture 12 through which the filament wire 3 extends. I

The filament wire 3 is disposed in one of the two focuses of a cylindrical reflector 7 having an elliptic cross-section, namely, in the focus F1 as illustrated in FIGURE 2. The cylindrical reflector 7 is affixed to the support 10 with the aid of an angle member 11. The reflector 7 is open on the side opposite to the filament wire 3, the reflector being cut open in such a way that its edges are parallel to the longitudinal axis of the reflector and approximately coincide with the parameter p passing through the focus F2 as shown in FIGURE 2.

The bimetallic strip 6 is arranged in the second focus P2 of reflector 7, and substantially closes the reflector on this side so that, except for a very small air flow through the slots between the bimetallic strip 6 and the reflector 7, no convective flow of the air is possible.

The bimetallic strip 6 is fixed to the plate 8 in such a way that the bimetallic strip is bent off from the reflector 7 when heated; i.e., the metal with the higher expansion coefficient is on the side facing the reflector, while the metal with the lower expansion coefficient is on the opposite side.

When current flows through the filament wire 3 the wire emits heat uniformly to all sides. The wire can be heated up to such an extent that it emits visible light. Only a small portion of the emitted heat energy directly hits the bimetallic strip 6. The major portion is distributed on the inside layer of the reflector 7. This reflector concentrates the heat radiation, arriving from the focus F1 at which the filament wire is located, in the focus F2 through which the metallic strip passes as illustrated in FIGURE 2. Around this point a zone of quasi heat intensity is obtained. Under the effect of this concentrated heat radiation, which heats only the side of the bimetallic strip facing the filament wire, the bimetallic strip '6 is bent off from the reflector 7 and thus from the contacting spring 5, thereby obtaining two different effects. First, the bimetallic strip is no longer in the hot zone. Second, the reflector now has two slot-like apertures between the bimetallic strip and the longitudinal edges of the reflector.

, These apertures now permit an increased convection of the air circulating in the reflector. At the same time a portion of the heat radiation can penetrate into the surrounding space through the increased slots. Besides, a portion of the heat stored in the metallic strip with the higher expansion coeflicient is transferred to the other strip of the bimetallic strip 6 and from there is emitted to its surroundings, whereby the first strip is cooled down quickly. With the aid of these effects, the bimetallic strip is cooled again. Consequently, it returns into its original position, constantly rendering its previously received heat energy to the ambient air. It is therefore possible to have the filament wire switched on, but it is also possible to lead the current of the filament through a switching contact of the relay and to simultaneously use that part of the filament 3 which projects beyond the reflector 7 as a light source; i.e., the light source is provided by that portion of the filament from Which the radiating beams do not serve to heat the bimetallic strip. Thus, a blinking light source is obtained by means of a very simple construction.

FIGURE 4 illustrates the construction of a thermal relay as described above wherein the filament wire, bimetallic strip and contact arrangement is accommodated in a glass tube 16. The glass tube 16 has two functions. First, it forms a hermetically sealed chamber for the relay, and second, it has an elliptic cross-section carrying a reflecting layer on its inside surface. Thus, no additional reflector is required. The bimetallic strip 6 is arranged for contact with a contacting lug 15 at the inner end of a lead 17 which extends through the glass bulb sealing 18 at one end of the bulb. A similar lead extending through the sealing at the other end of the glass bulb supports the bimetallic strip 6, and the filament wire 3 is supported between a pair of similar leads extending through the sealing at the opposite ends of the bulb.

FIGURE 5 illustrates the mounting of the relay arrangement on a dielectric socket 19 of the type which is conventional for incandescent bulbs. In this case, four of the leads 17 extend through the dielectric socket 19, two of the leads supporting the filament wire 3, one of the leads supporting the contacting lug 1S thereon, and the other lead supporting the bimetallic strip 6 thereon. This whole arrangement may be surrounded by a glass bulb 20 as shown in FIGURE 6, supplemented by a screwtype socket or a bayonet-lock socket, so as to provide a handy construction of a blink lamp, provided the filament 3 is somewhat longer than the reflector 7 and is connected in series with the switching contact. The contact then interrupts the filament circuit and closes the circuit again as described above.

While the instant invention has been shown and described herein in what are conceived to be the most practical and preferred embodiments, it is recognised that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

What is claimed is:

1. A beam-heated thermal relay which comprises a reflector having a cylindrical inside reflecting surface of generally elliptical cross-section, an elongated filament, and a temperature-sensitive contact including a bimetallic strip, said filament and bimetallic strip being disposed generally parallel to the longitudinal axis of said reflecting surface and proximate the respective oppositely located focuses of the ellipse.

2. A thermal relay according to claim 1, wherein said reflector is open on the side of the ellipse at which the bimetallic strip is located, the edges of the reflector at the opening being substantially parallel to the longitudinal axis of the reflector and approximately coinciding with the parameter passing through the respective focus of the ellipse.

3. A thermal relay according to claim 1, wherein the metal of said bimetallic strip with the higher expansion coeflicient faces the interior of the ellipse, and

4. A thermal relay according to claim 3, wherein the surface of the bimetallic strip which faces the interior of the ellipse is blackened.

5. A thermal relay according to claim 1, wherein said filament is a freely suspended filament Wire.

6. A thermal relay according to claim 1, wherein the relay arrangement is hermetically sealed by a glass enclosure.

7. A thermal relay according to claim 6, wherein the of said tube having a reflective coating thereon which provides said inside reflecting surface.

References Cited FOREIGN PATENTS 217,872 3/1941 Switzerland.

BERNARD A. GILHEANY, Primary Examiner inside of said glass enclosure is substantially free of 10 R. L. COHRS, Assistant Examiner oxygen.

8. A thermal relay according to claim 6, wherein said glass enclosure comprises a tube having a generally elliptical cross-section, at least a portion of the inside surface U.S. Cl. X.R. 

